Substantial use has been made of shipping containers which are repeatedly used to contain a product in transit and then returned empty for further re-use. For reasons of shipping volume economy alone it is obvious that containers which are collapsible for return and reuse have many advantages over containers of fixed, non-collapsible design. This collapsibility is not so difficult to achieve in a rectangular shipping container; however the problem becomes much more complex in its application to cylindrical containers such as drums or barrels. But the latter frequently have structural advantages as shipping containers over rectangular designs, more particularly in terms of unit stress conditions in the loaded container, which makes their use desirable in many instances. Prior cylindrical containers, unless made of highly flexible film or the like and therefore subject to easy rupture or puncture, have not been capable of being collapsed for empty-return. The approach to the problem, rather, has been in terms of nesting designs which offer only a partial solution.
The present invention provides a container of drum or cylinder configuration which possesses all of the desirable characteristics of a fixed drum or barrel type previously available, including the use of puncture resistant semi-rigid fiberboard side wall construction, but which unlike such prior drum or barrel types is collapsible into a flat condition for empty-return and repeated reuse cycling.